1. A longitudinal study is planned of the neuropsychological test performance of a group of cocaine abusers, who have been abstinent for eight days, to determine impairment in functioning, by comparing their performance with that of a matched non-drug control group. These two groups (now) [26 to 33] years of age), will be non-treatment community black subjects who had been studied intensively in the National Collaborative Perinatal Project (NCPP), from birth to seven years of age. Thus, the comprehensive pre-substance use data will be available to control for the effects of long-term cocaine use. Also, systematic school record data on these subjects, from when they were 13 to 15 years of age (California Achievement Test Scores, grades and attendance records during the 9th grade) will be available from the Philadelphia School District, to utilize as additional pre-substance use controls. 2. Two groups of hospitalized cocaine abusers will be assessed at two different time periods on the same neuropsychological test procedures as the community non-treatment groups above, and will be compared on their performance with matched control groups. One of these inpatient groups will be assessed at 8 days and 22 days of abstinence, and the other will be assessed at 8 days and 35 days of abstinence. These inpatient cocaine groups will all have used cocaine for at least three years, and they will be diagnosed as cocaine abusers by DSM-III-R and SCID. Cocaine will be their primary drug problem, and they will only have used alcohol, marijuana or other illicit substances to a limited extent (as will the community groups referred to above). It will be determined whether any deficit in functioning that is found for cocaine abusers is related to the duration of abstinence for cocaine.